The embodiments described herein relate to syringes and methods for administering a dose of medicament based on the subject's weight, height, age, or other characteristic.
Some known syringes for delivering dosages of a medicament include a syringe barrel with graduated markings and a plunger that is movable within the barrel to set the dosage and deliver the medicament. The graduated markings for such known syringes are often volumetric (i.e., they indicate the volume of the medicament within the syringe), and thus a user must calculate, convert, or otherwise determine the correct dose based on, among other things, the patient's weight, height and/or age. Additionally, the graduated markings are often very small, are sometimes provided in confusing or unfamiliar units of measure (e.g., teaspoons or milliliters), and require that the user align the plunger along the axis of motion to set the dosage. Moreover, certain medication regimens require that different amounts of the medicament be administered on different days of the treatment. Accordingly, using such known syringes and methods can result in an unacceptable level of medication error and/or “adverse drug events” because of improper dosing (delivering more or less of a drug than the prescribed amount), noncompliance with the regimen (missing a day, administering the improper amount for a given day), or the like.
Although such issues are prevalent with oral delivery of over-the-counter drugs, such as ibuprofen, Tylenol®, cough syrup, or the like, studies have shown that such issues also exist in hospital and clinical settings. For example, one study of adverse drug events at hospitals estimated that although a large number of adverse drug events occurred at the ordering stage, many occurred at the administering stage. Bates, D. W., et al., “Incidence of Adverse Drug Events and Potential Adverse Drug Events,” Journal of the American Medical Association, Jul. 5, 1995, Vol. 274, No. 1, pp. 29-30. Another study evaluating the ability of 100 registered nurses to calculate the correct dosage for oral, intramuscular, and intravenous drugs showed an average error rate of about 20 percent or higher, depending on the type of delivery mechanism. Bindler, et al., “Medication Calculation Ability of Registered Nurses,” Journal of Nursing Scholarship, 1991, 23:221-224.
One proposed solution to reduce medication error and/or “adverse drug events” is to deliver a predetermined dosage via a single-use prefilled syringe or cartridge. Although convenient for some drugs and/or therapeutic regimens, prefilled syringes are expensive, cumbersome to store, and impractical for many drugs (e.g., over-the-counter painkillers). Moreover, unless a caregiver maintains an inventory of prefilled syringes tailored to a variety of different patients (e.g., weight, age range, or the like), the use of prefilled syringes will still require that the user calculate, convert or otherwise determine the correct dose to be administered.
Other delivery devices for administering dosages, such as insulin pens, include dose-setting mechanisms that include rotatable caps or plungers, bulky multi-part container holders, and the like. Although these devices may be suitable for certain drugs and/or therapeutic regimens, such as chronic care situations (e.g., delivery of insulin), such known devices are impractical for many other drugs and/or therapeutic regimens. For example, administering an over-the-counter cold medicine via an expensive pen injector that requires adherence to specific instructions for use is impractical.
Thus, a need exists for improved methods and devices for easily and accurately delivering medicaments via a syringe.